1. Field of the Invention
The present invention magnetic tape head cleaning apparatus generally relates to the field of cleaning equipment, and more particularly to cleaning equipment adapted to be used for cleaning magnetic tape heads.
2. Description of the Prior Art
The increased use of magnetic tape as a source for entertainment and other purposes has resulted in a need for more efficient ways to maintain the equipment. The cassette tape playback/recording units being used within automobiles and other applications have several characteristics in common. The units which utilize cassette mounted tapes use a standardized cassette package. In addition, the cassette is inserted within an aperture or within a fully covered receiving area in the playback/recording unit, which unit is designed to prevent direct access to the magnetic tape head or the capstan and pinch roller which provides the motive force to the tape.
It has long been recognized that continued use of a playback/recording unit will result in the accumulation of dirt or other debris at the magnetic tape head, erase head, capstan and pinch roller. The accumulation of dirt or other debris results in degraded reproduction from or recording of the magnetic tape because of interference at the head gap. If left alone, this can result in a failure of the playback/recording unit.
The difficulty in gaining access to the magnetic tape head has lead to the development of devices which are disclosed by the prior art, none of which satisfactorily solve all of the inherent problems. One of the devices disclosed by the prior art uses a tape cartridge having an abrasive material mounted in place of the tape. The cleaning action of the magnetic tape heads is mechanical in nature and is intended to abrasively rub all dirt or debris from the fact of the magnetic tape head. The problem with this type of device is apparent. The magnetic tape head is a sensitive component made of small subcomponents, and contacting the surface of the magnetic tape head with an abrasive tape can eventually result in damage and possible destruction of the magnetic tape head.
Another device disclosed by the prior art incorporates a mounted felt strip within a magnetic tape cassette. The felt strip is urged through the cassette in the same manner as magnetic tape. The device is intended to clean the magnetic tape head by impregnating the felt strip with isopropyl alcohol or other like cleaning fluid and allows the movement of the felt strip across the magnetic tape head to clean dirt and other debris from the magnetic tape head. Several problems remain unsolved through the use of this device. Since the felt is mounted within the tape cassette to move therethrough in a manner analogous to tape, there is a substantial volume of felt material. This results in the cleaning fluid being defused substantially throughout the felt. The result is a very weak concentration of the cleaning fluid at the point of contact with the magnetic head, thus thereby minimizing the cleaning effect of the device. Another problem resides in an inability to apply sufficient pressure on the tape head to carry out the cleaning function. Since the felt strip is mounted in a manner analogous to the magnetic tape, significant pressure cannot be asserted against the strip to force it against the magnetic head. Such pressure would in effect stop the rotation of the capstan or otherwise halt the movement of the strip through the cassette and thereby prevent any cleaning action.
Another prior art device is disclosed in U.S. Pat. No. 3,761,994 (1973), which discloses a spring biased cleaning apparatus for magnetic tape cartridges. The inability to utilize a structure such as this is evident. An arm is disposed from the front to the rear wall of the cartridge a manual handle moves of the cleaning pads laterally across the magnetic tape head. The inadequacies of this device as applied to magnetic tape cassettes is evident. Since the cassette playback/recording units include an internal, covered compartment into which the magnetic tape cassette is inserted during operation, the movement of the cleaning member must be self-contained as there is no access to the internal members of the cassette.
Another device disclosed by the prior art is Applicant's U.S. Pat. No. 4,141,053 (1979). This device discloses a pair of spring biased arms which are rotatable about the hubs of the conventional housing. The present invention improves upon the device taught therein by utilizing a direct drive between the gear receiving the capstan surface and the cleaning head.
The present invention substantially solves those problems left unresolved by the devices disclosed in the prior art. Although the industry has attempted to maintain strict standards with respect to magnetic tape playback/recording units, it is well known that there is a variation of commercially available units, e.g., whether they are provided with or without tape guides. The positioning of tape guides can render many of the devices disclosed by the prior art useless for the intended purposes. In addition, any variation in the placement of the magnetic tape head capstan roller and device can also lead to inoperability of a cleaning device. The need for cleaning the magnetic tape head arises out of the structure of the magnetic tape head itself. The magnetic tape head assembly involved typically comprises separate heads for the particular number of recorded tracks of the tape being used. Each magnetic head is typically constructed of two identical core halves built of thin laminations of magnetic alloy material. Each half is then wound precisely with an identical number of turns and assembled with non-magnetic separators at the front and rear with a miniscule gap remaining at the bottom of the head which contacts the magnetic tape. As the tape transport draws the tape across the head, the gap between the core halves is shunted, and the magnetic flux path is completed. The head gap is critical in both the recording and reproduction phase of the process. When recorded tape is drawn across the gap of the head, the portion of the tape in actual contact with the gap bridges the magnetic core of the head causing magnetic flux to flow through the core. The head gap size depends on the intended function of the head. For a record head, it must be wide enough to permit the flux to penetrate the tape deeply, yet narrow enough to obtain sharp gradients of flux. For a reproduction head, gap size must be a compromise between the upper-frequency limit, dynamic range and head life. Extremely close mechanical tolerances are inherent in the head gap as well as the flux position of the tape and magnetic head. If dirt or other debris lodges on the surface of the magnetic tape head or within the head gap, the strength of the magnetic flux will be deleteriously affected. Therefore, in order to maintain proper operating conditions, the magnetic tape head must be cleaned to remove any dirt or debris which accumulates. These conditions will occur from the scraping effect which exists as the top oxide layer passes over the tape head. The oxide build-up and dirt and debris physically disposed on the magnetic tape are all contributing factors to reduced tape head operation.
Tape transports utilizing cassette mounted magnetic tape present a different problem with regard to cleaning the magnetic tape head assembly. Magnetic tape cassettes are generally mounted with apertures which substantially preclude access to the magnetic tape heads or are mounted within compartments which preclude any access to any of the lateral edges of the cassette. Since the magnetic tape head is virtually inaccessible, the need for the present invention has arisen.
The present invention utilizes three independently rotatable arms which are resiliently biased in a manner which will permit cleaning of both the tape head and the capstan drive. The arms are resiliently biased about three independent points within the cassette housing independent of the cassette housing. The capstan drive is urged against a geared surface having a surface which will rotate about its axis at the speed of the capstan drive. A planar gear transfers the rotation thereof to the capstan cleaning head, the resilient forces imposed on the gear train and the arms holding same maintaining appropriate forces against the tape head. The magnetic tape head will be subjected to sufficient cleaning motion irrespective of minor variations in the placement of the capstan roller and drive and the presence or absence of the guides.
The present invention comprises an apparatus for providing means to clean the magnetic tape head assembly of a playback/recording unit adapted for mounting tape cassettes. It is to be noted that the present invention can be adapted for cleaning the magnetic tape heads of eight-track cartridge transports, but for the purpose of example, cassette equipment shall be discussed.